1. Field
At least some example embodiments of the following description relate to a method of processing an image based on an orthogonal transform.
2. Description of the Related Art
In recent times, developments in smart phone technology has led to growth in authentication applications implemented using a face of a user for authentication. However, authentication using the user face is highly susceptible to complex illumination conditions indoors or outdoors. For example, when a user face is unidentifiable due to dark environments or shadows, an issue may arise authenticating the user face.
Accordingly, a method of generating a facial image of a gradient face has been proposed to solve this issue. The method of generating the facial image of the gradient face includes generating a gradient facial image using an arctan value with respect to a gradient ratio of a horizontal/vertical direction. In the method of generating the facial image of the gradient face, smoothing is performed on an input image for stability in gradient calculation, and a gradient value is calculated using a difference of Gaussian (DoG) operator.